Related Applications
This application is related to copending U.S. patent applications:
Ser. No. 824,925, entitled RANGE SECTION PROTECTION VALVE ASSEMBLY;
Ser. No. 824,924, entitled AUXILIARY SECTION ACTUATOR CONTROL SYSTEM AND METHOD;
Ser. No. 824,673, entitled INTERLOCK MECHANISM FOR RANGE SECTION SLAVE VALVE;
Ser. No. 824,675, entitled RANGE VALVE PRE-EXHAUST;
Ser. No. 824,961, entitled TWO-STAGE RANGE PISTON/CYLINDER ASSEMBLY;
Ser. No. 824,645, entitled VARIABLE PRESSURE RANGE SECTION ACTUATOR PISTON;
Ser. No. 824,960, entitled DUAL PRESSURE REGULATOR;
Ser. No. 824,672, entitled VARIABLE PRESSURE RANGE SECTION ACTUATOR ASSEMBLY;
Ser. No. 824,957, entitled AUXILIARY SECTION ACTUATOR AIR CONTROL SYSTEM;
Ser. No. 824,638, entitled RANGE SECTION ACTUATOR CONTROL SYSTEM AND METHOD FOR PREVENTING DAMAGE TO RANGE SECTION SYNCHRONIZERS; and
all assigned to the same assignee, Eaton Corporation, and filed the same day, Jan. 23, 1992, as this application.
1. Field of the Invention
The present invention relates to a control system or method for controlling the auxiliary section actuator of a vehicular compound transmission. In particular, the present invention relates to a control system or method for protecting the auxiliary section synchronized splitter jaw clutches, especially the splitter section high speed synchronized jaw clutches, of a compound heavy duty vehicular transmission.
2. Description of the Prior Art
Compound change gear transmissions of the type having one or more auxiliary sections connected in series with a main transmission section are very well known in the prior art. Such transmissions are typically associated with heavy duty vehicles such as large trucks, tractor/semi-trailers, and the like. Briefly, by utilizing main and auxiliary transmission sections connected in series, assuming proper relative sizing of the ratio steps, the total of available transmission ratios is equal to the product of the main and auxiliary section ratios. By way of example, at least in theory, a compound change gear transmission comprising a four (4) speed main section connected in series with a four (4) speed auxiliary section will provide sixteen (4.times.4=16) available ratios.
Auxiliary transmission sections are of three general types: range type, splitter type or combined range/splitter type.
In compound transmissions having a range type auxiliary section, the range section ratio step or steps are greater than the total ratio coverage of the main transmission section and the main section is shifted progressively through its ratios in each range. Examples of compound transmissions having range type auxiliary sections may be seen by reference to U.S. Pat. Nos. 4,974,474; 4,964,313, 4,920,815; 3,105,395; 2,637,222 and 2,637,221, the disclosures of which are hereby incorporated by reference.
Assignee's well known RT/RTO 11609 and RT/RTO 11610 "Roadranger" transmissions are examples of a "(4+1).times.(2)", nine speed and "(5).times.(2)" ten speed heavy duty range type transmissions.
In compound transmissions having a splitter type auxiliary section, the ratio steps of the splitter auxiliary section are less than the ratio steps of the main transmission section and each main section ratio is split, or subdivided, by the splitter section. Examples of compound change gear transmissions having splitter type auxiliary sections may be seen by reference to U.S. Pat. Nos. 4,290,515; 3,799,002; 4,440,037 and 4,527,447, the disclosures of which are hereby incorporated by reference.
In a combined range and splitter type auxiliary section, or sections, both range and splitter type ratios are provided allowing the main section to be progressively shifted through its ratios in at least two ranges and also allowing the main section ratios to be split in at least one range.
One example of a compound transmission having a single combined range/splitter type auxiliary section may be seen by reference to U.S. Pat. Nos. 3,283,613; 3,648,546, the disclosures of which are hereby incorporated by reference. A three gear layer, four-speed combined splitter/range type auxiliary section may be seen by reference to U.S. Pat. No. 4,754,665, the disclosure of which is hereby incorporated by reference. Assignee's well known RT/RTO 11613 and RT/RTO 14718 "Eaton Roadranger" transmissions are examples of a "(4+1).times.(3)" thirteen-speed and a "(4+1).times.(4)" eighteen-speed combined range/splitter type transmission.
Another example is the "Ecosplit" model of transmission sold by Zahnradfabrik Friedrichshafen Aktiengeseushaft of Friedrichshafen, Federal Republich of Germany which is a "(2.times.4.times.2)" sixteen forward speed type of transmission and utilizes a separate two-speed two-speed splitter auxiliary section in front of, and a separate range auxiliary section behind, the main transmission section.
It should be noted that the terms main and auxiliary sections are relative and that if the designations of the main and auxiliary sections are reversed, the type of auxiliary section (either range or splitter) will also be reversed. In other words, given what is conventionally considered a four-speed main section with two-speed range type auxiliary section, if the normally designated auxiliary is considered the main section, the normally designated main section would be considered a four-speed splitter type auxiliary section therefor. By generally accepted transmission industry convention, and as used in this description of the invention, the main transmission section of a compound transmission is that section which contains the largest (or at least no less) number of forward speed ratios, which allows section of a neutral position, which contains the reverse ratio(s) and/or which is shifted (in manual or semiautomatic transmissions) by manipulation of a shift bar or shift rail or shift shaft/shift finger assembly as opposed to master/slave valve/cylinder arrangements or the like.
In compound transmissions of the range or the combined range/splitter or splitter/range types, the main transmission section is typically shifted by means of a shift bar housing assembly, or single shift shaft assembly, controlled by a manually operated shift lever or the like and the auxiliary range section is shifted, in "repeat H" type transmissions, by means of button or switch, usually manually operated, which controls a remote slave valve/actuator mechanism. In so-called "double H" or "one and one-half H" type controls, the range is shifted by switches responsive to positioning of the shift lever. Double H type controls are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,633,725 and 4,275,612, the disclosures of which are incorporated hereby by reference.
In certain splitter sections, especially front splitter sections, the splitter section utilizes synchronized jaw clutches. Accordingly, to provide acceptable shift quality and prevent undue wear and/or damage to the splitter section synchronized jaw clutches, it has been an object of the prior art to provide devices to assure that a splitter shift be initiated and hopefully completed while the main disconnect coupling, such as a master clutch or torque converter disconnect clutch, is disengaged.
In view of the above, the prior art compound synchronized splitter type transmissions usually include a control system, usually a pneumatic control system, including interlock devices, which allowed a splitter shift to be preselected by use of a selector button or switch at a master control valve but not initiated until the disconnect is disengaged and which exhausted the splitter actuator wherever the disconnect was reengaged. Such systems typically utilized interlocks of the mechanical type on the splitter section actuator mechanical linkage which physically prevented movement of the splitter section shift fork until the disconnect device was disengaged and/or of the dump valve type wherein the valve (often called the "slave valve") supplying pressurized air to the splitter section pistons is not provided with pressurized fluid until and/or unless disengagement of the disconnect device is sensed.
While the prior art systems do provide considerable protection for the splitter section synchronizers by preventing initiation of a splitter shift and/or deenergizing the splitter shift actuators when the disconnect device is engaged, they are not totally satisfactory as while they assure that a splitter section shift will not initiate and/or proceed while the disconnect (master clutch) is engaged, they will not retain the splitter in a given position and are thus subject to splitter clutch slip out. Further, if the master clutch is reengaged prior to completion of a splitter shift, the transmission will be hung up in neutral and a second master clutch disengagement operation will be required.
As is well known, under certain conditions, if the splitter synchronized clutch attempts to engage while master clutch is engaged, a portion of the engine torque may be transferred to the vehicular drive wheels entirely by the engaged synchronizer friction surfaces and the synchronizer friction members, especially the high speed splitter synchronizer, can be rapidly damaged.